A “cell cycle” means a cycle wherein the period for a cell to divide and once again divide is one cycle, and this cycle is also referred to as a “cell division cycle”.
A cell cycle includes four phases in a determined order. They are DNA duplication preparation phase (G1 phase), DNA duplication phase (S phase), division preparation phase (G2 phase) and division phase (M phase), and regulated by many factors. Among them, the kinase activity of a cyclin/cyclin dependent kinase (CDK) complex is essential for the regulation of the cell cycle.
As a protein to inhibit the kinase activity, a CDK inhibitory protein is known. The CDK inhibitory proteins of mammalian cells are p21 family and p16 family, both of which are considered to negatively regulate the progress of cell cycle and responsible for cell differentiation, apoptosis and repair of DNA damage due to irradiation of X ray and the like. At present, p21, p27 and p57 have been reported as a p21 family, and p16, p15, p18 and p19 have been reported as a p16 family.
When these CDK inhibitory proteins are highly expressed in the cell, the cell proliferation is arrested at G1 phase.
The p21 family shows an inhibitory activity on a relatively wide range and plural cyclin/CDK complexes. For example, cyclin E/CDK 2 which is an important cyclin/CDK complex from G1 phase to G1/S transition phase, cyclin B/Cdc2 which is important for M phase and the like can be mentioned. The p16 family is a specific inhibitory factor against cyclin D/CDK 4 and cyclin D/CDK 6, which are one of the cyclin/CDKs in the G1 phase, and is considered to dissociate the cyclin/CDK complex by binding with CDK 4 and CDK 6, respectively.
From the examination of clinical materials of cancer of esophangus, pancreatic cancer, non-small cell lung cancer, skin cancer and the like, highly frequent incidence of genetic abnormality of P16 has been reported, and high cancer incidence in p16 knock out mice has been demonstrated, and therefore, clinical application of p16 inducer has been tried.
Under such situation, p15 protein (aka: INK4B, also simply referred to as p15) has been found as a p16 family. In 1994, induction of p15 expression by TGF-β stimulation was confirmed in human keratinocyte cell (HaCaT), and p15 was considered to be one of the factors negatively regulating the cell cycle. It is known that induction of G1 phase cell cycle arrest in HaCaT by TGF-β leads to the suppression of cell proliferation (Letters to Nature, Sep. 15, 1994, vol. 371, pp. 257-261).
While the histondeacetylase (HDAC) inhibitor is known to arrest cell cycles at G1 phase or G2 phase in human cancer cell, it has been found recently that trichostatin A, which is an HDAC inhibitor, induces p15 gene in human colon cancer cell (HCT116p21(−/−)), and the induction of p15 by trichostatin A is involved in the inhibition of the cell proliferation of the cancer cells (FEBS Letters, 2003, vol. 554, pp. 347-350).
In this way, a compound that induces p15 and/or p27 is expected to inhibit the cell proliferation of cancer cells and the like.
In the meantime, Mitogen-activated protein (MAP) Kinase/extracellular signal-regulated kinase (ERK) kinase (hereinafter to be referred to as MEK) is known to be involved in the regulation of cell proliferation as a kinase that mediates Raf-MEK-ERK signal transduction pathway, and the Raf family (B-Raf, C-Raf etc.) activates the MEK family (MEK-1, MEK-2 etc.) and the MEK family activates the ERK family (ERK-1 and ERK-2).
Activation of Raf-MEK-ERK signal transduction pathway in cancer, particularly colorectal cancer, pancreatic cancer, lung cancer, breast cancer and the like, has been frequently observed.
In addition, since the signals produced by signal molecules such as growth factor, cytokine and the like converge to the activation of MEK-ERK, inhibition of these functions is considered to more effectively suppress Raf-MEK-ERK signal transduction than the suppression of the function of RTK, Ras, Raf and the like in the upstream.
Moreover, it is also known in recent years that a compound having an MEK inhibitory activity extremely effectively induces inhibition of ERK1/2 activity and suppression of cell proliferation (The Journal of Biological Chemistry, vol. 276, No. 4, pp. 2686-2692, 2001), and the compound is expected to show effects on the disease caused by undesirable cell proliferation, such as tumor and the like. In addition, an MEK inhibitor is expected to inhibit infiltration or metastaticity of cells via promotion of expression of Matrix metalloproteinase (MMP) and CD44, and angiogenesis via promotion of expression of vascular endothelial growth factor (VEGF).
Furthermore, application to chronic pain (JP 2003-504401: WO 01/005393), application to diseases or symptoms mediated by neutrophile (JP2002-332247: CA-2385412), application to graft rejection (JP 2002-532414: WO 00/35435), application to arthritis (JP 2002-532415: WO 00/35436), application to asthma (JP 2002-534380: WO 00/40235), application to viral diseases (JP 2002-534381: WO 00/40237), application to diseases caused by deformation or injury of cartilage (WO2002/087620; US 2004/138285), application to Peutz-Jeghers syndrome (WO02/006520) are expected.
However, such pharmaceutical agent has not been marked heretofore.
As an already commercially available antitumor agent, the following compound (Gefitinib) and the like are known (Iressa tablet 250 package insert).

JP-A-2004-504294 (patent family: WO2002/006213) describe the following compound and the like as compounds having an antitumor activity. In addition, the MEK inhibitory activity of such compounds is described (JP-A-2004-504294, pp. 123-124, Example 39, Example 241).

Known compounds relatively similar to the pharmaceutical agent of the present invention are described below.
In the literatures issued in 1991, the antitumor activity of pyrido[2,3-d]pyrimidine derivative has been studied and it is described, for example, that some of the following compounds and the like have an inhibitory activity in sarcoma, leukemia cells (Khimiia geterotsiklicheskikh soedinenii, 1991, No. 5, pp. 674-680 (English translation p. 542, lines 4-7; p. 538, compound IIIa)).

In the literatures issued in 1973, novel synthetic methods of the following compound and the like are disclosed and the antitumor activity of pyrido[2,3-d]pyrimidine derivative is described (Chem. Pharm. Bull., 1973, No. 21, vol. 9, pp. 2014-2018 (p. 2015, chart 2, compound VIII)).

In these literatures, however, the compound of the present invention is not disclosed, nor is there found a description suggestive thereof.
Furthermore, WO2002/094824 discloses the following compound and the like (WO2002/094824, p. 55, Example 9) as a therapeutic agent having a cytokine regulating action for immune, inflammatory or allergic disease.

In the literatures issued in 1996, synthetic methods of the following compound and the like are disclosed (Journal fur Praktische Chemie, 1996, vol. 338, pp. 151-156 (p. 154, Table 1, compound 8f)).

In the literatures issued in 1986, synthetic methods of the following compound and the like as a synthetic intermediate for aminopterin analog having an antitumor activity are disclosed (Journal of Medicinal Chemistry, 1986, vol. 29, No. 5, pp. 709-715 (p. 709 abstract; p. 712, Table 1, compound 9b)).

However, this literature does not contain a description relating to the use of these compounds as antitumor agents, the compound of the present invention is not disclosed and a description suggestive thereof is not found.